Insulating CMU behind baseboard heaters

Hey guys,

I have a dilema here. I'm currently working on remodeling some semi-below grade walls. The walls were wood panel(press board), and very thin. Beneath the panel was double sided foil barrier stapled to 1/2" furring strips running vertical to a bottom strip of wood 1/2"x11"x12', and a top strip of wood, 1/2"x4"x12'.
The thing is the foil didnt reach to the bottom of the baseboard heater, just 1" below. Also the bottom strip of wood didnt reach the floor. It sits on top of small blocks of wood used to attach the baseboard heater to the wall(crazy, I know).
I removed the panel and some of the foil barrier, but not the wood yet.
I'm hoping for recommendations on insulating the walls completly behind the baseboard heaters.
I'm thinking i have 1" of space behind the heaters. Removing them is not an option.